MESOSCALE PRECIPITATION DISCUSSION 0533
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1115 PM EDT TUE SEP 29 2015
 
AREAS AFFECTED...EASTERN PA...NJ...SOUTHEAST NY...CT...WRN MA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 300315Z - 300815Z
 
SUMMARY...INCREASING HEAVY RAINS AND EMBEDDED CONVECTION AIDED BY
WELL DEFINED MESO LOW LIFTING NEWD FROM NORTHERN MARYLAND LIKELY
TO LEAD TO FLASH FLOODING.

DISCUSSION...SFC/RADAR IMAGERY SHOWS A WELL DEFINED MESO LOW
CIRCULATION OVER NORTHERN MARYLAND RIDING NORTHEASTWARD ALONG
RIBBON OF WEAK INSTABILITY TOWARD SOUTHEAST PENNSYLVANIA. 
SATELLITE IMAGERY CONTINUES TO SHOW FAIRLY COLD TOP CONVECTION
WITH AND TO THE NORTHEAST OF THIS SYSTEM.  THE LOW ITSELF IS
HELPING PROVIDE INCREASING MOISTURE CONFLUENCE/LIFT IN AN
OTHERWISE IMPRESSIVE TROPICAL MOISTURE REGIME WELL IN ADVANCE OF A
SYNOPTIC COLD FRONT ACROSS THE OH VALLEY.  SATELLITE AND GPS PWS
INDICATE PWS AS HIGH AS 2.5 INCHES EAST OF THE LOW CIRCULATION AND
THE COMBINATION OF THE VERY HIGH MOISTURE...TALL SKINNY
CAPES...AND ENHANCED CONVERGENCE WITH THE LOW WILL CONTINUE TO
LEAD TO SOME VERY IMPRESSIVE LOCALIZED HEAVY RAINFALL RATES. 
RECENT STORM HISTORY HAS SHOWN RAINFALL RATES OF 2 TO 3 INCHES PER
HOUR ACROSS PARTS OF CENTRAL MARYLAND WITH SOME 3 HOURLY RATES
OVER 5 INCHES.

EXPECT THE HEAVIER RAINS WITH EMBEDDED CONVECTIVE CELLS TO
CONTINUE TO LIFT NEWD ACROSS ERN PA..NJ..SE NY..INTO WRN CT BASED
ON 12Z RUNS OF THE WRF ARW AND NSSL WRF WHICH APPEAR TO HAVE THE
BEST HANDLE ON SHORT TERM TRENDS.  

SULLIVAN

ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI...

ATTN...RFC...MARFC...NERFC...

LAT...LON   42887337 41847284 40507380 39877435 39767501 
            39827546 39877555 40307576 41137586 42077509 
            42697436